Adaptive Multi-Mode Charging

ABSTRACT

An apparatus is disclosed for adaptive multi-mode charging. In an example aspect, the apparatus includes at least one charger having a first node and a second node. The at least one charger is configured to accept an input voltage at the first node. The at least one charger is also configured to selectively operate in a first mode to generate a first output voltage at the second node that is greater than or less than the input voltage or operate in a second mode to generate a second output voltage at the second node that is substantially equal to the input voltage.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit of U.S. Provisional Application No.62/951,876, filed 20 Dec. 2019, the disclosure of which is herebyincorporated by reference in its entirety herein.

TECHNICAL FIELD

This disclosure relates generally to battery charging and, morespecifically, to a charger that can operate in multiple modes.

BACKGROUND

Batteries are reliable, portable energy sources that are used by a widerange of electronic devices including mobile phones, laptops, toys,power tools, medical device implants, electronic vehicles, andsatellites. A battery, however, stores a fixed amount of charge that isdepleted during mobile operation of the electronic device. Instead ofrequiring the purchase of a replacement, many batteries are rechargeablevia another power source. The same battery can therefore be usedmultiple times.

An electronic device can include a charger to recharge the battery. Thecharger is designed to provide a particular voltage or current that isappropriate for charging the battery. Thus, the charger enables atransfer of power between, for instance, an adaptor that is plugged intoa wall socket and the battery. By including the charger in the device,it is easier for a user to recharge the battery during the day as theuser moves around. Unfortunately, incorporating into an electronicdevice a charger that can handle different charging scenarios ischallenging.

SUMMARY

Apparatuses and techniques are disclosed that implement adaptivemulti-mode charging. In particular, an example single charger canselectively operate as a charge pump (e.g., a voltage divider-typecharge pump or a voltage multiplier-type charge pump), as a directcharger (e.g., a pass-through charger or a bypass charger), or anothertype of charger with a different conversion ratio. The charger can alsoselectively provide forward charging or reverse charging. With theability to operate in different modes, the charger can support bothwired and wireless charging. The charger can also be used to chargesingle-cell or multi-cell batteries.

In some situations, the multi-mode charger dynamically switches betweendifferent modes to optimize efficiency for different operatingtemperatures and loads. The charger can also be implemented to supportdifferent types of adaptors. Use of the example multi-mode chargerobviates the need for implementing additional chargers within theapparatus, which can conserve space and reduce cost of the apparatus.Furthermore, any protection functions or features can be active for thedifferent modes of the charger. Some apparatuses can include multiplemulti-mode chargers to support multi-phase charging or multi-cellbattery charging.

In an example aspect, an apparatus is disclosed. The apparatus includesat least one charger having a first node and a second node. The at leastone charger is configured to accept an input voltage at the first node.The at least one charger is also configured to selectively operate in afirst mode to generate a first output voltage at the second node that isgreater than or less than the input voltage or operate in a second modeto generate a second output voltage at the second node that issubstantially equal to the input voltage.

In an example aspect, an apparatus is disclosed. The apparatus includessupply means for providing an input voltage and load means for acceptingan output voltage. The apparatus also includes charging means fortransferring power from the supply means to the load means byselectively providing a first voltage as the output voltage inaccordance with a first mode or a second voltage as the output voltagein accordance with a second mode. The first voltage is greater than orless than the input voltage and the second voltage is substantiallyequal to the input voltage.

In an example aspect, a method for adaptive multi-mode charging isdisclosed. The method includes operating a charger as avoltage-divider-type charge pump or a voltage-multiplier-type chargepump during a first time interval. The operating the charger during thefirst time interval comprises accepting a first input voltage at a firstnode of the charger and generating, based on the first input voltage, afirst output voltage at a second node of the charger. The first outputvoltage is less than or greater than the input voltage based on thecharger operating as the voltage-divider-type charge pump or thevoltage-multiplier-type charge pump, respectively. The method alsoincludes operating the charger as a direct charger during a second timeinterval. The operating the charger during the second time intervalcomprises accepting a second input voltage at the first node of thecharger and generating, based on the second input voltage, a secondoutput voltage at the second node of the charger. The second outputvoltage is substantially equal to the second input voltage based on thecharger operating as the direct charger.

In an example aspect, an apparatus is disclosed. The apparatus includesat least one power supply circuit, at least one load, at least onebattery, a switching circuit coupled to the at least one power supplycircuit and the at least one load, and at least one charger. The atleast one charger comprises a first node coupled to the switchingcircuit and a second node coupled to the at least one battery. The atleast one charger is configured to selectively transfer power from theat least one power supply circuit to the at least one battery based onthe switching circuit connecting the at least one power supply circuitto the first node or transfer power from the at least one battery to theat least one load based on the switching circuit connecting the at leastone load to the first node.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates an example environment for adaptive multi-modecharging.

FIG. 2 illustrates example power transfer circuitry for adaptivemulti-mode charging.

FIG. 3 illustrates an example charger for adaptive multi-mode charging.

FIG. 4-1 illustrates an example voltage-divider forward-charging mode ofa charger for adaptive multi-mode charging.

FIG. 4-2 illustrates an example direct forward-charging mode of acharger for adaptive multi-mode charging.

FIG. 4-3 illustrates an example voltage-multiplier reverse-charging modeof a charger for adaptive multi-mode charging.

FIG. 4-4 illustrates an example direct reverse-charging mode of acharger for adaptive multi-mode charging.

FIG. 5 illustrates example implementations of a switching circuit and acharger for adaptive multi-mode charging.

FIG. 6 illustrates example power transfer circuitry with multiplechargers coupled together in parallel for adaptive multi-mode charging.

FIG. 7 illustrates example power transfer circuitry with multiplechargers to provide adaptive multi-mode charging for a multi-cellbattery.

FIG. 8 illustrates another example charger for adaptive multi-modecharging.

FIG. 9 illustrates an example protection circuit for adaptive multi-modecharging.

FIG. 10 is a flow diagram illustrating an example process for performingadaptive multi-mode charging.

DETAILED DESCRIPTION

An electronic device can include a charger to recharge the battery. Thecharger is designed to provide a particular voltage or current that isappropriate for charging the battery. Thus, the charger enables atransfer of power between, for instance, an adaptor that is plugged intoa wall socket and the battery. By including the charger in the device,it is easier for a user to recharge the battery during the day as theuser moves around. Unfortunately, incorporating into an electronicdevice a charger that can handle different charging scenarios ischallenging.

Different types of chargers can be designed to perform under differentoperating conditions. For example, some chargers operate at highefficiency while providing a large charging current to the battery, andothers operate at high efficiency while providing a small chargingcurrent to the battery. Additionally, some chargers can be used withdifferent types of adaptors or can accept a wide range of inputvoltages.

Each of these different types of chargers are designed for a specificoperating condition. Consequently, each individual charger type isunable to dynamically adapt to changes in the operating conditions. Toaddress this, some techniques may implement multiple chargers within theelectronic device and then enable an appropriate charger according to acurrent operating condition. Including multiple chargers can, however,increase a size and cost of the electronic device.

To address this, an apparatus is disclosed that implements adaptivemulti-mode charging. In particular, the apparatus includes a multi-modecharger that can selectively operate as a charge pump (e.g., a voltagedivider-type charge pump or a voltage multiplier-type charge pump), as adirect charger (e.g., a pass-through charger or a bypass charger), oranother type of charger with a different conversion ratio. The chargercan also selectively provide forward charging or reverse charging. Withthe ability to operate in different modes, the charger can support bothwired and wireless charging. The charger can also be used to chargesingle-cell or multi-cell batteries.

In some situations, the multi-mode charger dynamically switches betweendifferent modes to optimize efficiency for different operatingtemperatures and loads. The charger can also be implemented to supportdifferent types of adaptors. Use of the charger obviates the need forimplementing additional chargers within the apparatus, which canconserve space and reduce cost of the apparatus. Furthermore, anyprotection functions or features can be active for the different modesof the charger. Some apparatuses can include multiple multi-modechargers to support multi-phase charging or multi-cell battery charging.

FIG. 1 illustrates an example environment 100 for adaptive multi-modecharging. In the example environment 100, an example computing device102 receives power from a power source 104 or provides power to anexternal load 105. The power source 104 can represent any type of powersource, including a power outlet, a solar charger, a portable chargingstation, a wireless charger, another battery, and so forth. The externalload 105 can represent an external peripheral, such as a headset oranother computing device (e.g., another smartphone). In this example,the computing device 102 is depicted as a smartphone. However, thecomputing device 102 can be implemented as any suitable computing orelectronic device, such as a modem, a cellular base station, a broadbandrouter, an access point, a cellular phone, a gaming device, a navigationdevice, a media device, a laptop computer, a desktop computer, a tabletcomputer, a wearable computer, a server, a network-attached storage(NAS) device, a smart appliance or other internet of things (IoT)device, a medical device, a vehicle-based communication system, a radar,a radio apparatus, and so forth.

As illustrated, the computing device 102 can includes at least one powersupply circuit 106, at least one load 108, and power transfer circuitry110. Example types of power supply circuits 106 include a wireless powerreceiver 112, a power adaptor 114, or a battery 116. As an example, thepower adaptor 114 can include a universal serial bus (USB) adaptor.Depending on the type of computing device 102, the battery 116 maycomprise a lithium-ion battery, a lithium polymer battery, anickel-metal hydride battery, a nickel-cadmium battery, a lead acidbattery, and so forth. The battery 116 can also include a single-cellbattery, a multi-cell battery (e.g., a two-cell battery), or multiplebatteries, such as a main battery and a supplemental battery.

In some cases, the power supply circuit 106 jointly operates with theexternal power source 104 to provide power to the computing device 102.For example, the wireless power receiver 112 provides wireless chargingusing the external power source 104, which can include a wireless powertransmitter of another device. As another example, the power adaptor 114provides wired charging using the external power source 104, which caninclude the power outlet.

The load 108 is internal to the computing device 102. Example types ofloads include the power adaptor 114, the battery 116, or a wirelesspower transmitter 118. Other example loads 108 include a fixed load, avariable load, or a load associated with a component of the computingdevice 102, such as an application processor, an amplifier within awireless transceiver, or a display (not shown in FIG. 1). In some cases,the load 108 provides power to the external load 105. For example, thewireless power transmitter 118 provides wireless charging for theexternal load 105, which can include a wireless power receiver ofanother device. As another example, the power adaptor 114 provides wiredcharging to the external load 105, which can include a battery ofanother device.

The power transfer circuitry 110 of the computing device 102 includesone or more power paths 120-1 to 120-N, at least one switching circuit122, and at least one charger 124. The variable N represents a positiveinteger. The power transfer circuitry 110 can transfer power from one ormore power sources (e.g., the external power source 104 or the powersupply circuit 106) to one or more loads (e.g., the external load 105 orthe load 108). This power is transferred along one or more power paths120-1 to 120-N, which couple the one or more power sources or one ormore loads to the switching circuit 122.

The switching circuit 122 can provide isolation for individual powerpaths 120-1 to 120-N. For example, the switching circuit 122 can isolateone of the power paths 120-1 to 120-N from the battery 116 to preventleakage current from flowing from the battery 116 to one of the powerpaths 120-1 to 120-N. For implementations that include multiple powerpaths 120-1 to 120-N, the switching circuit 122 can enable individualpower paths 120 to be connected to the charger 124 and provide isolationbetween the power paths 120-1 to 120-N.

The charger 124 implements, at least partially, adaptive multi-modecharging. The charger 124 includes at least one flying capacitor 126 andswitches 128-1 to 128-S, where S represents a positive integer. Theflying capacitor 126 and the switches 128-1 to 128-S are furtherdescribed with respect to FIGS. 3 and 8. The charger 124 can beimplemented on a stand-alone integrated circuit or as part of apower-management integrated circuit (PMIC), which implements additionalfunctions.

The charger 124 can operate in different modes, which enables thecharger 124 to operate as a charge pump (e.g., a voltage divider-typecharge pump or a voltage multiplier-type charge pump) or a directcharger. In some cases, a conversion ratio of the charger 124 can varyfor different modes. For example, the charge pump can implement adivide-by-two charge pump that provides a 2:1 conversion ratio, amultiply-by-two charge pump that provides a 1:2 conversion ratio, or adirect charger that provides a 1:1 conversion ratio.

Generally, the charger 124 can implement a divide-by-N charge pump or amultiply-by-N charge pump, where N represents a positive integer (e.g.,1, 2, 3, or 4). Some types of chargers 124 can operate with additionalconversion ratios, such as a 1:3 conversion ratio, a 3:1 conversionratio, a 2:3 conversion ratio, a 3:2 conversion ratio, a 1:4 conversionratio, a 4:1 conversion ratio, a 2:4 conversion ratio, a 4:2 conversionratio, and so forth. Some modes can enable the charger 124 to performforward charging, and other modes can enable the charger 124 to performreverse charging. These modes are further described below.

The power transfer circuitry 110 also includes at least one mode-controlcircuit 130 and at least one protection circuit 132. The mode-controlcircuit 130 can include a bias voltage generator (not shown in FIG. 1),which generates different bias voltages based on a software or hardwarecommand. These bias voltages, which can establish different switchstates, control a mode of the charger 124 and a configuration of theswitching circuit 122. By providing different bias voltages, themode-control circuit 130 can dynamically change the mode of the charger124 as the operating conditions change.

The protection circuit 132 can provide a variety of protections,including input under-voltage lock-out, input over-voltage lock-out,surge protection, input current limit regulation, input peak currentlimit, battery overvoltage, battery overcurrent, programmable die and/orskin thermal regulation, die thermal shutdown, reverse currentprotection, input short protection, output short protection,input-to-output voltage ratio monitoring, or some combination thereof.In some implementations, thresholds associated with the protectioncircuit 132 can be adjusted based on an operational mode of the charger124. For example, the input-to-output voltage ratio monitoring can havean expected voltage ratio adjusted based on whether the charger 124operates as a voltage divider-type charge pump or a voltagemultiplier-type charge pump. The expected voltage ratio can also beadjusted as the charger 124 operates in different modes that providedifferent conversion ratios. Some protection circuits 132 can bedesigned to provide protection during both forward charging and reversecharging. In this case, the protection circuits 132 can be designed tosense currents that flow in a forward direction from the power path 120to the battery 116 and currents that flow in a reverse direction fromthe battery 116 to the power path 120. Various types of protectioncircuits 132 are further described with respect to FIG. 9.

In some implementations, the power transfer circuitry 110 includes amain charger (not shown), which can be implemented in parallel with thecharger 124. In this case, the charger 124 can operate as a slavecharger while the main charger operates as a master charger. The powertransfer circuitry 110 is further described with respect to FIG. 2.

FIG. 2 illustrates example power transfer circuitry 110 for adaptivemulti-mode charging. In the depicted configuration, the power transfercircuitry 110 is coupled to the wireless power receiver 112, the poweradaptor 114, the wireless power transmitter 118, and the battery 116.Although not explicitly shown, the power transfer circuitry 110 can alsoinclude an output capacitor coupled in parallel with the battery 116.

The power transfer circuitry 110 includes a first power path 120-1, asecond power path 120-2, and a third power path 120-3. The first powerpath 120-1 couples the wireless power receiver 112 to the switchingcircuit 122. The second power path 120-2 couples the power adaptor 114to the switching circuit 122. The third power path 120-3 couples thewireless power transmitter 118 to the switching circuit 122.

The switching circuit 122 is coupled between the power paths 120-1 to120-3 and the charger 124. The switching circuit 122 includes a firstswitch 202-1, a second switch 202-2, and a third switch 202-3. The firstswitch 202-1 selectively connects or disconnects the wireless powerreceiver 112 to the charger 124. Likewise, the second switch 202-2selectively connects or disconnects the power adaptor 114 to the charger124. The third switch 202-3 selectively connects or disconnects thewireless power transmitter 118 to the charger 124. The charger 124 iscoupled between the switching circuit 122 and the loads 108-1 and 108-2.

The mode-control circuit 130 is coupled to the switching circuit 122 andthe charger 124. During operation, the mode-control circuit 130generates a power-path control signal 204, which controls states of theswitches 202-1 to 202-3. With the power-path control signal 204, themode-control circuit 130 can enable power to be transferred between thecharger 124 and any one of the power paths 120-1 to 120-3. Themode-control circuit 130 also generates a mode-control signal 206, whichcontrols a mode of the charger 124.

As described above, each mode can be associated with a particularconversion ratio and charging direction. A mode that supports forwardcharging 208 enables power to transfer from one of the power paths 120-1or 120-2 to the charger 124. Another mode that supports reverse charging210 enables power to transfer from the charger 124 to one of the powerpaths 120-2 or 120-3. For example, power can be transferred from thewireless power receiver 112 or the power adaptor 114 to the battery 116during forward charging 208. In contrast, power can be transferred fromthe battery 116 to the power adaptor 114 or the wireless powertransmitter 118 during reverse charging 210. As described above, thebattery 116 can act as the load 108 during forward charging 208 or canact as the power supply circuit 106 during reverse charging 210.Likewise, the power adaptor 114 can act as the power supply circuit 106during forward charging 208 or can act as the load 108 during reversecharging 210. Both the power-path control signal 204 and themode-control signal 206 can include multiple bias voltages, which biasthe gate voltage of transistors that implement the switches 202-1 to202-3 and the switches 128-1 to 128-S of the charger 124 (shown in FIG.1). The charger 124 is further described with respect to FIG. 3.

FIG. 3 illustrates an example charger 124 for adaptive multi-modecharging. In the depicted configuration, the charger 124 is implementedas a divide-by-two charge pump or a multiply-by-two charge pump, whichcan provide a conversion ratio of 2:1 or 1:2, respectively. Otherimplementations can include a divide-by-three charge pump, adivide-by-four charge pump, or a divide-by-N charge pump.

The charger 124 includes a node 302, another node 304, and a ground node306. The node 302 is coupled to the switching circuit 122. The othernode 304 is coupled to the battery 116. For forward charging 208, thenode 302 operates as an input node and the node 304 operates as anoutput node. Alternatively, for reverse charging 210, the node 304operates as the input node and the node 302 operates as the output node.

The charger 124 includes the flying capacitor 126 (C_(Fly) 126), whichis coupled to a positive node 308 (CP 308) and a negative node 310 (CN310). The charger 124 also includes four switches 128-1 to 128-4. Theswitches 128-1 to 128-4 can be implemented using transistors, such asmetal-oxide-semiconductor field-effect transistors (MOSFETs), junctionfield-effect transistors (JFETs), bipolar junction transistors (BJTs),insulated gate bipolar transistors (IGBTs), diodes, and so forth. Anexample implementation of the switches 128-1 to 128-4 is furtherdescribed with respect to FIG. 5.

The first switch 128-1 (S1 128-1) is coupled between the positive node308 and the node 302. The second switch 128-2 (S2 128-2) is coupledbetween the negative node 310 and the node 304. The first switch 128-1and the second switch 128-2 can operate together to form a chargingcircuit, which charges the flying capacitor 126.

The third switch 128-3 (S3 128-3) is coupled between the ground node 306and the negative node 310. The fourth switch 128-4 (S4 128-4) is coupledbetween the positive node 308 and the node 304. The third switch 128-3and the fourth switch 128-4 can operate together to form a dischargingcircuit, which discharges the flying capacitor 126. The charger 124 ofFIG. 3 can operate as a divide-by-two charge pump, a multiply-by-twocharge pump, or a direct charger to support forward charging 208 orreverse charging 210, as further described with respect to FIGS. 4-1 to4-4.

FIG. 4-1 illustrates an example voltage-divider forward-charging mode400-1 of the charger 124 for adaptive multi-mode charging. During thevoltage-divider forward-charging mode 400-1, the charger 124 operates asa voltage-divider-type charge pump to support forward charging 208. Inthe depicted configuration, the switches 128-1 to 128-4 are active. Inparticular, the switches 128-1 and 128-2 open and close according to acharging phase signal while the switches 128-3 and 128-4 open and closeaccording to a discharging phase signal. During this mode, the charger124 provides a conversion ratio of 2:1. In other words, the charger 124generates an output voltage 404 at the node 304 that is half an inputvoltage 402 at the node 302. In this mode, an output current that flowsto the battery 116 is twice an input current that flows into the node302. By increasing the output current relative to the input current, thecharger 124 can reduce a time it takes to charge the battery 116.

During operation, the switching circuit 122 can connect the wirelesspower receiver 112 or the power adaptor 114 to the node 302. Inparticular, the switch 202-1 (of FIG. 2) can be closed and the switches202-2 and 202-3 (of FIG. 2) can be open to connect the wireless powerreceiver 112 to the node 302 and isolate both the power adaptor 114 andthe wireless power transmitter 118 from the node 302. Alternatively, theswitches 202-1 and 202-3 can be opened and the switch 202-2 can beclosed to connect the power adaptor 114 to the node 302 and isolate boththe wireless power receiver 112 and the wireless power transmitter 118from the node 302.

The voltage-divider forward-charging mode 400-1 enables the charger 124to operate at a high efficiency while providing a large current to thebattery 116. The voltage-divider forward-charging mode 400-1 can be usedwhile the power transfer circuitry 110 operates within a particularthermal or current threshold. To manage the temperature, the charger 124can dynamically switch to a direct forward-charging mode 400-2, asfurther described in FIG. 4-2.

FIG. 4-2 illustrates an example direct forward-charging mode 400-2 ofthe charger 124 for adaptive multi-mode charging. During the directforward-charging mode 400-2, the charger 124 operates as a directcharger to support forward charging 208. In the depicted configuration,the first switch 128-1 and the fourth switch 128-4 are closed (e.g., ina closed state) while the second switch 128-2 and the third switch 128-3are opened (e.g., in an open state). During this mode, the charger 124provides a conversion ratio of 1:1. In other words, the charger 124generates an output voltage 404 at the node 304 that is substantiallyequal to (e.g., within approximately 90% of) an input voltage 402 at thenode 302. In this mode, the output current that flows to the battery 116is substantially equal to an input current that flows into the node 302.During operation, the switching circuit 122 can connect the wirelesspower receiver 112 or the power adaptor 114 to the node 302.

The direct forward-charging mode 400-2 enables the charger 124 tooperate at a high efficiency while providing a small current to thebattery 116. Although this can increase the time it takes to charge thebattery 116, the temperature within the power transfer circuitry 110 candecrease. In general, the charger 124 can dynamically switch between thedirect forward-charging mode 400-2 and the voltage-dividerforward-charging mode 400-1 of FIG. 4-1 to manage temperature of thepower transfer circuitry 110 while decreasing charging times.

For example, the mode-control circuit 130 can monitor a temperatureassociated with the computing device 102, such as a temperatureassociated with the power supply circuit 106, the load 108, or the powertransfer circuitry 110. If the monitored temperature exceeds a firstthreshold, the mode-control circuit 130 causes the charger 124 totransition from the voltage-divider forward-charging mode 400-1 to thedirect forward-charging mode 400-2, to enable the temperature todecrease. If the monitored temperature drops below a second threshold,the mode-control circuit 130 causes the charger 124 to transition thedirect forward-charging mode 400-2 to the voltage-dividerforward-charging mode 400-1.

FIG. 4-3 illustrates an example voltage-multiplier reverse-charging mode400-3 of the charger 124 for adaptive multi-mode charging. During thevoltage-multiplier reverse-charging mode 400-3, the charger 124 operatesas a voltage-multiplier-type charge pump to support reverse charging210. In the depicted configuration, the switches 128-1 to 128-4 areactive. In particular, the switches 128-1 and 128-2 open and closeaccording to a charging phase signal while the switches 128-3 and 128-4open and close according to a discharging phase signal. During thismode, the charger 124 provides a conversion ratio of 1:2. In otherwords, the charger 124 generates an output voltage 404 at the node 302that is twice an input voltage 402 at the node 304. In this mode, anoutput current that flows into the switching circuit 122 is half aninput current that flows into the node 304 from the battery 116.

This mode enables power to be transferred from the battery 116 to theexternal load 105 using the power adaptor 114 of the power path 120-2 orthe wireless power transmitter 118 of the power path 120-3. Duringoperation, the switching circuit 122 can connect the power adaptor 114or the wireless power transmitter 118 to the node 302. Thevoltage-multiplier reverse-charging mode 400-3 enables the charger 124to support high-power reverse wireless or wired charging without relyingon additional components or chargers.

FIG. 4-4 illustrates an example direct reverse-charging mode 400-4 ofthe charger 124 for adaptive multi-mode charging. During the directreverse-charging mode 400-4, the charger 124 operates as a directcharger to support reverse charging 210. In the depicted configuration,the first switch 128-1 and the fourth switch 128-4 are closed while thesecond switch 128-2 and the third switch 128-3 are opened. During thismode, the charger 124 provides a conversion ratio of 1:1. In otherwords, the charger 124 generates an output voltage 404 at the node 302that is substantially equal to an input voltage 402 at the node 304. Inthis mode, an output current that flows to the switching circuit 122 issubstantially equal to an input current that flows into the node 304from the battery 116. During operation, the switching circuit 122 canconnect the power adaptor 114 of the power path 120-2 or the wirelesspower transmitter 118 of the power path 120-3 to the node 302. Thedirect reverse-charging mode 400-4 enables the charger 124 to supportlow-power reverse wireless or wired charging without relying onadditional components or chargers.

In some cases, the computing device 102 can send a command to the powertransfer circuitry 110 or the mode-control circuit 130 to enable one ofthe reverse-charging modes 400-3 or 400-4. In other cases, the powertransfer circuitry 110 (or the mode-control circuit 130) canautomatically activate reverse charging. As an example, the powertransfer circuitry 110 can activate one of the reverse-charging modes400-3 or 400-4 responsive to determining that no input power is presentand determining that the battery voltage is sufficient for reversecharging. For reverse wireless charging, the power transfer circuitry110 can activate one of the reverse-charging modes 400-3 or 400-4responsive to receiving a wireless signal from the other device'swireless receiver.

In general, the charger 124 can dynamically switch between the directreverse-charging mode 400-4 and the voltage-multiplier reverse-chargingmode 400-3 of FIG. 4-3 to manage temperature of the power transfercircuitry 110 while decreasing charging times. In order to switchbetween different modes 400-1 to 400-4, the power transfer circuitry 110may implement a soft-start process that gradually adjusts a voltage atone of the power paths 120-1 to 120-3 to avoid providing a large initialcurrent.

FIG. 5 illustrates example implementations of the switching circuit 122and the charger 124 for adaptive multi-mode charging. In the depictedconfiguration, the switches 202-1 and 202-3 (of FIG. 2) and the switches128-1 to 128-4 (of FIG. 3) are implemented using MOSFETs. The MOSFETsare in a common-gate configuration, which enables power to transfer ineither direction across the other terminals (e.g., across the sourceterminal and the drain terminal). The switches 202-1 to 202-3 and 128-1to 128-4 also include respective diodes coupled between the source anddrain terminals. The mode-control circuit 130 is coupled to the gates ofthese MOSFETs and provides respective bias voltages to the gates. Thebias voltages cause the switches 202-1 to 202-3 to respectively connectthe power paths 120-1 to 120-3 to the charger 124. Other bias voltagescause the switches 128-1 to 128-4 to open or close according to one ofthe modes 400-1 to 400-4 described above.

FIG. 6 illustrates example power transfer circuitry 110 with multiplechargers 124-1 and 124-2 for adaptive multi-mode charging. In thedepicted configuration, the chargers 124-1 and 124-2 are coupledtogether in parallel. The mode-control circuit 130 provides a firstmode-control signal 206-1 to the charger 124-1 and a second mode-controlsignal 206-2 to the charger 124-2. The chargers 124-1 and 124-2 canoperate in any of the modes 400-1 to 400-4 described above. In somecases, the chargers 124-1 and 124-2 operate with different phases, inorder to provide dual-phase charging. Other implementations can includemore than two chargers 124 to support multi-phase charging.

FIG. 7 illustrates example power transfer circuitry 110 with multiplechargers 124-1 to 124-2 to provide adaptive multi-mode charging for amulti-cell battery 116. In the depicted configuration, the powertransfer circuitry 110 includes a mater charger 702, which can becoupled to the wireless power receiver 112 and/or the power adaptor 114.

In FIG. 7, the chargers 124-1 and 124-2 are implemented in differentdirections. For example, the node 302 of the charger 124-1 (shown as302-1) is coupled to the switching circuit 122 and the node 304 of thecharger 124-1 (shown as 304-1) is coupled to the battery 116. Incontrast, the node 302 of the charger 124-2 (shown as 302-2) is coupledto the battery 116 and the node 304 of the charger 124-2 (shown as304-2) is coupled to the master charger 702 and the load 108. By havingopposite nodes 304-1 and 302-2 coupled to the battery 116, the charger124-1 can operate as a voltage divider-type charge pump for forwardcharging 208 and the charger 124-2 can operate as a voltage divider-typecharge pump for reverse charging 210. Additionally, the charger 124-1can operates as a voltage-multiplier-type charge pump for reversecharging 210 and the charger 124-2 can operate as avoltage-multiplier-type charge pump for forward charging 208. Thecharger 124-2 can also operate in the direct forward-charging mode 400-3or the direct reverse-charging mode 400-4 (of FIGS. 4-3 and 4-4).

In some implementations, the charger 124-1 implements a different typeof charge pump than the charger 124-2. This enables the chargers 124-1and 124-2 to provide different conversion ratios. Although not shown,the battery 116 can include two or more cells that are connectedtogether in series.

During operation, power can be transferred between either one of thepower paths 120-1 and 120-2 and the battery 116 using the charger 124-1or the charger 124-2. The master charger 702 can provide anotherconversion ratio to enable the charger 124-2 to support different typesof power adaptors 114 or different types of wireless power receivers112. The charger 124-2 can also transfer power from the battery 116 tothe load 108, which can include the wireless power transmitter 118.

FIG. 8 illustrates another example charger 124 for adaptive multi-modecharging. In the depicted configuration, the charger 124 can operate asa divide-by-four charge pump, a divide-by-two charge pump, amultiply-by-four charge pump, a multiply-by-two charge pump, or a directcharger to provide a conversion ratio of 4:1, 2:1 (or 4:2), 1:4, 1:2 (or2:4), or 1:1, respectively.

The charger 124 includes the node 302, the node 304, and the ground node306 (of FIG. 3). As described above, the node 302 operates as an inputnode and the node 304 operates as an output node for forward charging208. Alternatively, for reverse charging 210, the node 304 operates asthe input node and the node 302 operates as the output node.

The charger 124 includes multiple flying capacitors 126-1 to 126-5(C_(Fly) 126-1 to 126-5) and multiple switches 128-1 to 128-8. Nodes802-1 to 802-7 exist between respective pairs of the switches 128-1 to128-8. In particular, the node 802-1 is coupled between the first switch128-1 (S1 128-1) and the second switch 128-2 (S2 128-2), the node 802-2is coupled between the second switch 128-2 and the third switch 128-3(S3 128-3), the node 802-3 is coupled between the third switch 128-3 andthe fourth switch 128-4 (S4 128-4), the node 802-4 is coupled betweenthe fourth switch 128-4 and the fifth switch 128-5 (S5 128-5), the node802-5 is coupled between the fifth switch 128-5 and the sixth switch128-6 (S6 128-6), the node 802-6 is coupled between the sixth switch128-6 and the seventh switch 128-7 (S7 128-7), and the node 802-7 iscoupled between the seventh switch 128-7 and the eight switch 128-8 (S8128-8). The node 802-6 is the same as the node 304.

The flying capacitors 126-1 to 126-5 are coupled between different pairsof the nodes 802-1 to 802-7. In particular, the first flying capacitor126-1 is coupled between the node 802-1 and the node 802-3. The flyingcapacitor 126-2 is coupled between the node 802-3 and the node 802-5.The flying capacitor 126-3 is coupled between the node 802-5 and thenode 802-7. The flying capacitor 126-4 is coupled between the node 802-2and the node 802-4. The flying capacitor 126-5 is coupled between thenode 802-4 and the node 802-6.

The charger 124 of FIG. 8 can operate according to the voltage-dividerforward-charging mode 400-1. To provide a 4:1 conversion ratio betweenthe node 302 and the node 304 during the voltage-dividerforward-charging mode 400-1, the switches 128-1 to 128-8 alternatebetween open and closed states. In this mode, the charger 124 can alsoprovide a 2:1 conversion ratio between the node 302 and the node 802-4.In this case, the node 802-4 can be coupled to a load 108 within thecomputing device 102. Alternatively, the charger 124 can provide a 2:1conversion ratio between the node 302 and the node 802-4 by operatingthe switches 128-3 and 128-4 in the closed state and having the switches128-1, 128-2, 128-7, and 128-8 alternate between the open and closedstates.

Additionally or alternatively, the charger 124 can operate according tothe direct forward-charging mode 400-2 or the direct reverse-chargingmode 400-3 to provide a 1:1 conversion ratio between the node 302 andthe node 304. During either of these modes, the switches 128-1 to 128-6are in the closed state and the switches 128-7 and 128-8 are in the openstate.

Additionally or alternatively, the charger 124 can operate according tothe voltage-multiplier reverse-charging mode 400-4 to provide a 1:4conversion ratio between the node 304 and the node 302. During thismode, the switches 128-1 to 128-8 alternate between the open state andthe closed state. In this mode, the charger 124 can also provide a 1:2conversion ratio between the node 802-4 and the node 302. In this case,the node 802-4 can be coupled to a power supply circuit 106 within thecomputing device 102. Alternatively, the charger 124 can provide a 1:2conversion ratio between the node 304 and the node 302 by operating theswitches 128-3 and 128-4 in the closed state and having the switches128-1, 128-2, 128-7, and 128-8 alternate between the open and closedstates.

FIG. 9 illustrates an example protection circuit 132 for adaptivemulti-mode charging. In the depicted configuration, the protectioncircuit 132 can include an input under-voltage lock-out circuit 902, aninput over-voltage lock-out circuit 904, a surge protection circuit 906,an input current limit regulation circuit 908, an input peak currentlimit circuit 910, a batter over-voltage circuit 912, a batteryover-current circuit 914, a thermal regulation circuit 916, a thermalshutdown circuit 918, a reverse current protection circuit 920, an inputshort protection circuit 922, an output short protection circuit 922, orsome combination thereof.

The input under-voltage lock-out circuit 902 and the input over-voltagelock-out circuit 904 are coupled to the node 302 of the charger 124 andthe mode-control circuit 130. Each of these circuits 902 and 904 can beimplemented using a comparator (e.g., an operational amplifier). Theinput under-voltage lock-out circuit 902 and the input over-voltagelock-out circuit 904 jointly control operation of the mode-controlcircuit 130 based on an input voltage at the node 302. For example, theinput under-voltage lock-out circuit 902 compares the input voltage atthe node 302 to an under-voltage lock-out threshold, and the inputover-voltage lock-out circuit 904 compares the input voltage to anover-voltage lock-out threshold. If the input voltage is between theunder-voltage lock-out threshold and the over-voltage lock-outthreshold, the input under-voltage lock-out circuit 902 and the inputover-voltage lock-out circuit 904 allow the mode-control circuit 130 tooperate the charger 124 (e.g., enable the charger 124 to charge anddischarge the flying capacitor 126). Alternatively, if the input voltageis less than the under-voltage lock-out threshold or greater than theover-voltage lock-out threshold, the associated input under-voltagelock-out circuit 902 or the input over-voltage lock-out circuit 904prevents the mode-control circuit 130 from enabling the charger 124(e.g., prevents the mode-control circuit 130 from operating the switches128-1 to 128-S of the charger 124).

The surge protection circuit 906 is coupled to one of the power paths120-1 to 120-N. For example, the surge protection circuit 906 is coupledto the power path 120-2 of FIG. 2. The surge protection circuit 906 caninclude a diode, such as a transient-voltage-suppression (TVS) diode.Using the diode, the surge protection circuit 906 absorbs energy duringa surge event. This provides additional time for the input over-voltagelock-out circuit 904 to detect an over-voltage event.

The input current limit regulation circuit 908 is coupled to the node302 of the charger 124 and includes a current sensor and a comparator.Using the current sensor, the input current limit regulation circuit 908monitors the input current and compares an average of the input currentto an average current threshold. If the average of the input current isgreater than or equal to the average current threshold, the inputcurrent limit regulation circuit 908 limits the input current to thecharger 124 to protect the power adaptor 114.

The input peak current limit circuit 910 is coupled to the node 302 ofthe charger 124 and the mode-control circuit 130. In an exampleimplementation, the input peak current limit circuit 910 includes acurrent sensor and a comparator. Using the current sensor, the inputpeak current limit circuit 910 monitors the input current and compares apeak of the input current to a peak current threshold. If the peak ofthe input current is greater than or equal to the peak currentthreshold, the input peak current limit circuit 910 directs themode-control circuit 130 to power down the charger 124. In some cases,the input peak current limit circuit 910 can delay powering down thecharger 124 until the peak current threshold has been exceeded apredetermined number of times.

The battery over-voltage circuit 912 and the battery over-currentcircuit 914 are each coupled to the battery 116 and the mode-controlcircuit 130. The battery over-voltage circuit 912 includes a voltagesensor and a comparator to monitor a voltage across the battery 116.During operation, the battery over-voltage circuit 912 can direct themode-control circuit 130 to stop charging the flying capacitor 126 ofthe charger 124 if the voltage across the battery 116 is greater than orequal to an over-voltage threshold. By disabling the charging cycle, thebattery over-voltage circuit 912 can prevent the battery 116 from beingover charged.

The battery over-current circuit 914 includes a current sensor and acomparator to monitor an input current to the battery 116. The batteryover-current circuit 914 directs the mode-control circuit 130 to limitthe current provided to the battery 116 responsive to the current beinggreater than or equal to an over-current threshold. This ensures safecharging of the battery 116.

The thermal regulation circuit 916 is coupled to the power adaptor 114.During operation, the thermal regulation circuit 916 monitors a skinthermal of the power adaptor 114. If the skin thermal becomes greaterthan a thermal window, the thermal regulation circuit 916 directs thepower adaptor 114 to reduce the current provided to the charger 124 toenable the temperature to decrease. Alternatively, if the skin thermaldrops below the thermal window, the thermal regulation circuit 916directs the power adaptor 114 to increase the current to increasecharging efficiency.

The thermal shutdown circuit 918 is coupled to the charger 124 and themode-control circuit 130. The thermal shutdown circuit 918 monitors atemperature of the die associated with the charger 124. If the dietemperature becomes greater than or equal to a threshold, the thermalshutdown circuit 918 directs the mode-control circuit 130 to power downthe charger 124 until the die temperature drops below a predeterminedlevel.

The reverse current protection circuit 920 includes the switch 202-2 ofthe switching circuit 122, which is implemented between the poweradaptor 114 and the charger 124. The reverse current protection circuit920 detects when the power adaptor 114 is disconnected from the externalpower source 104 or the external load 105 and causes the switch 202-2 tobe in the open state to disconnect the power adaptor 114 from thecharger 124. In this way, the reverse current protection circuit 920 canprevent power from being transferred from the battery 116 to the poweradaptor 114.

The input short protection circuit 922 can include the switch 202-2.During operation, the input short protection circuit 922 detects a shortevent in which the power adaptor 114 or the power path 120-2 is shortedto ground. In this situation, the input short protection circuit 922causes the switch 202-2 to be in the open state to prevent the battery116 from discharging.

The output short protection circuit 924 detects a short event in whichthe node 304 is shorted to ground. The output short protection circuit924 includes a comparator to monitor the voltage at the node 304. If thevoltage at the node 304 is less than a threshold, such as two volts, theoutput short protection circuit 924 directs the mode-control circuit 130to power down the charger 124. This prevents the charger 124 fromdelivering a large current that can damage the battery 116.

FIG. 10 is a flow diagram illustrating an example process 1000 foradaptive multi-mode charging. The process 1000 is described in the formof a set of blocks 1002-1004 that specify operations that can beperformed. However, operations are not necessarily limited to the ordershown in FIG. 10 or described herein, for the operations may beimplemented in alternative orders or in fully or partially overlappingmanners. Operations represented by the illustrated blocks of the process1000 may be performed by the power transfer circuitry 110 (e.g., of FIG.1 or 2). More specifically, the operations of the process 1000 may beperformed by the charger 124 as shown in FIG. 3, 5, or 8.

At block 1002, a charger operates as a voltage-divider-type charge pumpor a voltage-multiplier-type charge pump during a first time interval.For example, the charger 124 operates as the voltage-divider-type chargepump or a voltage multiplier-type charge pump during a first timeinterval to support forward charging 208, as shown in FIG. 2.

At block 1004, a first input voltage is accepted at a first node of thecharger. For example, the charger 124 accepts the input voltage 402 atthe node 302, as shown in FIG. 4-1.

At block 1006, a first output voltage is generated at a second node ofthe charger. The first output voltage is based on the first inputvoltage. The first output voltage is less than or greater than the inputvoltage based on the charger operating as the voltage-divider-typecharge pump or the voltage-multiplier-type charge pump, respectively.For example, the charger 124 generates an output voltage 404 at the node304 that is less than or greater than the input voltage 402. As anexample, the charger 124 can operate according to the voltage-dividerforward-charging mode 400-1 of FIG. 4-1.

At block 1008, the charger operates as a direct charger during a secondtime interval. For example, the charger 124 operates as the directcharger during the second time interval to support forward charging 208,as shown in FIG. 2.

At block 1010, a second input voltage is accepted at the first node ofthe charger. For example, the charger 124 accepts the input voltage 402at the node 302, as shown in FIG. 4-2.

At block 1012, a second output voltage is generated at the second nodeof the charger. The second output voltage is based on the second inputvoltage and is substantially equal to the second input voltage based onthe charger operating as the direct charger. For example, the charger124 generates the output voltage 404 at the node 304 that issubstantially equal to (e.g., within 90% of) the input voltage 402 atthe node 302. As an example, the charger 1002 can operate according tothe direct forward-charging mode 400-2 of FIG. 4-2.

Additionally or alternatively, the charger can selectively operate asthe voltage-divider-type charge pump, the voltage-multiplier-type chargepump, or the direct charger to support reverse charging 210, as shown inFIG. 2, 4-3, or 4-4. In this case, the charger 124 can generate anoutput voltage 404 at the node 302 that is less than, greater than, orsubstantially equal to an input voltage 402 at the node 304. As anexample, the charger 124 can operate according to the voltage-multiplierreverse-charging mode 400-3 or the direct reverse-charging mode 400-4 ofFIGS. 4-3 and 4-4, respectively.

Unless context dictates otherwise, use herein of the word “or” may beconsidered use of an “inclusive or,” or a term that permits inclusion orapplication of one or more items that are linked by the word “or” (e.g.,a phrase “A or B” may be interpreted as permitting just “A,” aspermitting just “B,” or as permitting both “A” and “B”). Further, itemsrepresented in the accompanying figures and terms discussed herein maybe indicative of one or more items or terms, and thus reference may bemade interchangeably to single or plural forms of the items and terms inthis written description. Finally, although subject matter has beendescribed in language specific to structural features or methodologicaloperations, it is to be understood that the subject matter defined inthe appended claims is not necessarily limited to the specific featuresor operations described above, including not necessarily being limitedto the organizations in which features are arranged or the orders inwhich operations are performed.

What is claimed is:
 1. An apparatus comprising: at least one chargerhaving a first node and a second node, the at least one chargerconfigured to: accept an input voltage at the first node; andselectively: operate in a first mode to generate a first output voltageat the second node that is greater than or less than the input voltage;or operate in a second mode to generate a second output voltage at thesecond node that is substantially equal to the input voltage.
 2. Theapparatus of claim 1, wherein the at least one charger is configured toselectively: operate as a divide-by-n charge pump or a multiply-by-ncharge pump according to the first mode; or operate as a direct chargeraccording to the second mode.
 3. The apparatus of claim 1, wherein: thefirst output voltage is less than the input voltage; and the apparatusfurther comprises a mode-control circuit coupled to the at least onecharger, the mode-control circuit configured to: monitor a temperatureassociated with the apparatus; and cause the at least one charger totransition from operating in the first mode to operating in the secondmode responsive to the temperature being greater than a first threshold.4. The apparatus of claim 3, wherein the mode-control circuit isconfigured to cause the at least one charger to transition fromoperating in the second mode to operating in the first mode responsiveto the temperature being less than a second threshold, the secondthreshold being less than the first threshold.
 5. The apparatus of claim1, wherein: the apparatus comprises: at least one power supply circuitcoupled to the first node of the at least one charger; and at least oneload coupled to the second node of the at least one charger; and the atleast one charger is configured to transfer power from the at least onepower supply circuit to the at least one load based on the first mode orthe second mode.
 6. The apparatus of claim 5, wherein: the at least onepower supply circuit comprises at least one of: a wireless powerreceiver; a power adaptor; or a battery; and the at least one loadcomprises at least one of: the power adaptor; another battery; awireless power transmitter; a display of the apparatus; or a wirelesstransceiver of the apparatus.
 7. The apparatus of claim 5, wherein: theat least one power supply circuit comprises a first power supply circuitand a second power supply circuit; and the apparatus further comprises aswitching circuit coupled to the first power supply circuit, the secondpower supply circuit, and the first node of the at least one charger,the switching circuit configured to selectively: connect the first powersupply circuit to the first node of the at least one charger; or connectthe second power supply circuit to the second node of the at least onecharger.
 8. The apparatus of claim 1, wherein the at least one chargercomprises: a positive node and a negative node; a ground node; at leastone capacitor coupled between the positive node and the negative node; afirst switch coupled between the first node and the positive node; asecond switch coupled between the negative node and the second node; athird switch coupled between the negative node and the ground node; anda fourth switch coupled between the positive node and the second node.9. The apparatus of claim 8, wherein the at least one charger isconfigured to: actively switch states of the first switch, the secondswitch, the third switch, and the fourth switch between an open stateand a closed state for the first mode; place the first switch and thefourth switch in the closed state for the second mode; and place thesecond switch and the third switch in the open state for the secondmode.
 10. The apparatus of claim 1, wherein the at least one charger isfurther configured to: accept another input voltage at the second node;and selectively: operate in a third mode to generate a third outputvoltage at the first node that is greater than or less than the otherinput voltage; or operate in a fourth mode to generate a fourth outputvoltage at the first node that is equal to the other input voltage. 11.The apparatus of claim 10, wherein: the apparatus comprises: a firstpower supply circuit; a first load coupled to the second node of the atleast one charger; a second power supply circuit coupled to the secondnode of the at least one charger; a second load; and a switching circuitcoupled to the first power supply circuit, the second load, and thefirst node of the at least one charger, the switching circuit configuredto selectively: connect the first power supply circuit to the first nodeof the at least one charger; or connect the second load to the firstnode of the at least one charger; and the at least one charger isconfigured to selectively: transfer power from the first power supplycircuit to the first load based on the first mode or the second mode; ortransfer power from the second power supply circuit to the second loadbased on the third mode or the fourth mode.
 12. The apparatus of claim11, wherein: the first power supply circuit comprises a wireless powerreceiver or a power adaptor; the first load comprises a battery, adisplay of the apparatus, or a wireless transceiver of the apparatus;the second power supply circuit comprises the battery; and the secondload comprises a wireless power transmitter or the power adaptor. 13.The apparatus of claim 1, wherein: the at least one charger comprises afirst charger and a second charger coupled together in parallel; and thefirst charger is configured to provide a first conversion ratio for thefirst mode; and the second charger is configured to provide a secondconversion ratio for the first mode, the second conversion ratio beingdifferent than the first conversion ratio.
 14. The apparatus of claim 1,wherein: the at least one charger comprises a first charger and a secondcharger coupled together in parallel; the first charger is configured tooperate according to a first phase; the second charger is configured tooperate according to a second phase that is different than the firstphase; and the first charger and the second charger are configured tooperate together to provide dual-phase charging.
 15. The apparatus ofclaim 1, wherein: the at least one charger comprises a first charger anda second charger; the first charger is configured to operate in thefirst mode or the second mode to support forward charging; and thesecond charger is configured to operate in the first mode or the secondmode to support reverse charging.
 16. An apparatus comprising: supplymeans for providing an input voltage; load means for accepting an outputvoltage; and charging means for transferring power from the supply meansto the load means by selectively providing a first voltage as the outputvoltage in accordance with a first mode or a second voltage as theoutput voltage in accordance with a second mode, the first voltage beinggreater than or less than the input voltage, the second voltage beingsubstantially equal to the input voltage.
 17. The apparatus of claim 16,wherein: the first voltage is less than the input voltage; and theapparatus further comprises control means for directing the chargingmeans to selectively provide the first voltage responsive to atemperature associated with the apparatus being greater than a firstthreshold or provide the second voltage responsive to the temperaturebeing less than a second threshold, the second threshold being less thanthe first threshold.
 18. The apparatus of claim 16, further comprising:other supply means for providing the input voltage, wherein theapparatus further comprises switching means for selectively connectingthe supply means to the charging means or connecting the other supplymeans to the charging means.
 19. The apparatus of claim 16, wherein thecharging means comprises: a first node coupled to the supply means; asecond node coupled to the load means; a ground node coupled to aground; capacitive means for selectively storing or releasing energy;and switching means for selectively connecting the capacitive meansbetween the first node and the second node or connecting the capacitivemeans between the ground node and the second node.
 20. The apparatus ofclaim 19, further comprising: other supply means for providing anotherinput voltage, the other supply means coupled to the second node; andother load means for accepting another output voltage, the other loadmeans coupled to the first node, wherein the charging means isconfigured to transfer power from the other supply means to the otherload means by selectively providing a third voltage as the other outputvoltage in accordance with a third mode or a fourth voltage as the otheroutput voltage in accordance with a fourth mode, the third voltage beinggreater than or less than the other input voltage, the fourth voltagebeing equal to the other input voltage.
 21. The apparatus of claim 20,further comprising means for selectively acting as the load means or theother supply means.
 22. A method comprising: operating a charger as avoltage-divider-type charge pump or a voltage-multiplier-type chargepump during a first time interval, the operating the charger during thefirst time interval comprising: accepting a first input voltage at afirst node of the charger; and generating, based on the first inputvoltage, a first output voltage at a second node of the charger, thefirst output voltage being less than or greater than the input voltagebased on the charger operating as the voltage-divider-type charge pumpor the voltage-multiplier-type charge pump, respectively; and operatingthe charger as a direct charger during a second time interval, theoperating the charger during the second time interval comprising:accepting a second input voltage at the first node of the charger; andgenerating, based on the second input voltage, a second output voltageat the second node of the charger, the second output voltage beingsubstantially equal to the second input voltage based on the chargeroperating as the direct charger.
 23. The method of claim 22, furthercomprising: transferring power from a first power supply circuit coupledto the first node of the charger to a first load coupled to the secondnode of the charger during the first time interval and the second timeinterval; operating the charger as the voltage-divider-type charge pumpor the voltage-multiplier-type charge pump during a third time interval,the operating the charger during the third time interval comprising:accepting a third input voltage at the second node of the charger; andgenerating, based on the third input voltage, a third output voltage atthe first node of the charger, the third output voltage being less thanor greater than the third input voltage based on the charger operatingas the voltage-divider-type charge pump or the voltage-multiplier-typecharge pump, respectively; and transferring power from a second powersupply circuit coupled to the second node of the charger to a secondload coupled to the first node of the charger during the third timeinterval.
 24. The method of claim 23, further comprising: operating thecharger as the direct charger during a fourth time interval, theoperating the charger during the fourth time interval comprising:accepting a fourth input voltage at the second node of the charger; andgenerating, based on the fourth input voltage, a fourth output voltageat the first node of the charger, the fourth output voltage beingsubstantially equal to the fourth input voltage based on the chargeroperating as the direct charger; and transferring power from the secondpower supply circuit to the second load during the fourth time interval.25. An apparatus comprising: at least one power supply circuit; at leastone load; at least one battery; a switching circuit coupled to the atleast one power supply circuit and the at least one load; and at leastone charger comprising: a first node coupled to the switching circuit;and a second node coupled to the at least one battery, the at least onecharger configured to selectively: transfer power from the at least onepower supply circuit to the at least one battery based on the switchingcircuit connecting the at least one power supply circuit to the firstnode; or transfer power from the at least one battery to the at leastone load based on the switching circuit connecting the at least one loadto the first node.
 26. The apparatus of claim 25, wherein the at leastone charger is configured to selectively operate as avoltage-divider-type charge pump, a voltage-multiplier-type charge pump,or a direct charger.
 27. The apparatus of claim 26, wherein the at leastone charger is configured to selectively: operate as thevoltage-multiplier-type charge pump to transfer power from the at leastone power supply circuit to the at least one battery; or operate as thevoltage-divider-type charge pump to transfer power from the at least onebattery to the at least one load.
 28. The apparatus of claim 26, whereinthe at least one charger is configured to: operate as the direct chargerto transfer power from the at least one power supply circuit to the atleast one battery; or operate as the direct charger to transfer powerfrom the at least one battery to the at least one load.
 29. Theapparatus of claim 25, wherein: the at least one power supply circuitcomprises at least one of: a wireless power receiver; or a poweradaptor; and the at least one load comprises at least one of: the poweradaptor; or a wireless power transmitter.
 30. The apparatus of claim 25,wherein the at least one charger comprises: a positive node and anegative node; a ground node; at least one capacitor coupled between thepositive node and the negative node; a first switch coupled between thefirst node and the positive node; a second switch coupled between thenegative node and the second node; a third switch coupled between thenegative node and the ground node; and a fourth switch coupled betweenthe positive node and the second node.